I guess this is '267'?
Updating the 'Bou (
Three)
The most radical re-engining concept for the RAAF
Caribou fleet came as a Private Venture proposal from Hawker de Havilland Australia. In this scheme, the piston engined DHC-4s were to be transformed into STOL jet transports. The original
Caribou engines would be replaced by vectoring-thrust Rolls-Royce
Pegasus BE.53/2 turbofans in nacelles derived from those of the still-born Dornier Do 31E. [1]
HdH began work at its Bankstown NSW plant on a privately-procured DHC-4A to convert this airframe to '
Pegasus-
Caribou' standards. Other than changing nacelle mounts to suit the DHC-4A wing, the engine installation caused no real difficulties. The aircraft did require a completely new main undercarriage [2] and HdH initiated a series of other changes and improvements to their prototype conversion. These included a 'glass' cockpit; a throughly rebuilt nose section (incorporating both weather radar and an E/O turret); and, to improve slow-speed control, upswept wingtips and auxiliary tail surfaces attached to the horizontal tailplane. [2]
(
Top) Prototype '
Pegasus-
Caribou' conversion prior to completion
The finished DHC-4P '
Pegasus-
Caribou' conversion was unveiled at the 1988 Australian International Airshow at RAAF Richmond in NSW. The full performance of this prototype was not apparent as its underdeveloped main undercarriage was fixed in the 'down' position. However, some control problems had been revealed in slow-speed flying tests. The auxiliary tail surfaces proved to be much too small while the 'winglets' slowed rolling manoeuvres while hampering side-slipping. Standard DHC-4 wingtips were reintroduced and a series of different-sized experimental dorsal fins were introduced through the DHC-4P's flight testing phase.
Formal RAAF test flights were undertaken at RAAF Base Amberley - west of Brisbane - in the final configuration of the '
Pegasus-
Caribou' prototype. By this stage, the auxiliary fins had been removed and a very large fibreglass dorsal fin had been adopted. A production-type retractable main undercarriage was installed along with a fully-function E/O turret. [3] After testing, RAAF planners concluded that the '
Pegasus-
Caribou' was too complex and expensive to suit its requirement for a direct
Caribou replacement. However, the type showed great promise for a dedicated assault transport for special forces.
A new specification was drawn up to match the '
Pegasus-
Caribou' and orders issued for four aircraft with options for two more. To be known as the HdH-4P
SASR Caribou, the RAAF type differed from the prototype in retaining the standard DHC-4 nose and being 'equipped for but not fitted with' much of their potential upgrades. Provision was made for future installation of weather radar radomes and for the fitting of twin E/O turrets on either side of the cockpit. [4]
In late 1990, the first 'production'
SASR Caribou conversion was delivered to No 35 (Special Operations) Squadron based at RAAF Base Pearce, just north of Perth, WA. This basing was dictated by the Special Air Service Regiment (SASR) being located at Swanbourne, WA. No 35 SO would eventually receive all six HdH-4Ps just in time to be divided into two permanent detachments - 'Det A' remained at RAAF Pearce to support Tactical Assault Group (West) with three
SASR Caribou; 'Det B' went to RAAF Base Richmond north-west of Sydney to support the Tactical Assault Group (East). [5]
(
Bottom) HdH-4P
SASR Caribou in service with No 35 (SO) Squadron. This aircraft has Stage 3 upgrades including new nose radar, twin IAI POP200 E/O turrets installed, antennae fit, and defensive aid suite. [6]
________________________________________________________
[1] The German Do 31E was an experiment VTOL transport. Along with the thrust-vectoring
Pegasus turbofans, the Do 31E also had wingtip-mounted lift-jet engines to provide vertical take-off. The short take-off '
Pegasus-
Caribou' dispensed with such lift-jets.
[2] Tailoring the Rockwell 'glass' displays to the
Caribou cockpit was the responsibility of HdH Systems Division co-located with the DSTO at Salisbury, SA.
[3] This Wescam MX-10 E/O replaced the dummy turret used as an aerodynamic 'shape' during earlier trials.
[3] The object of this installation approach was to allow the flight crew to dedicate on E/O turret to cockpit displays while SOF used the second E/O for tactical purposes. Alternatively, both E/Os could be employed to widen the swath of ground imaging.
[4] The core of Tactical Assault Group (West) was, of course, the SASR. The core of Tactical Assault Group (East) was the newly-formed 1st Commando Regiment. 1 Cdo Regt was based out of Randwick Barracks, Sydney.
[5] DAS included AN/ALR-69A RWR antennae (on each each of nose and above engine nacelles), IR jammers (mounts above engine nacelles, but not fitted here), and IR flare bays in the rear of each engine nacelle.